UnsafePointer in Swift

Issue #130

Code is in Swift 4

Constructing UnsafeMutablePointer

let byteCount = 32
let result = UnsafeMutablePointer<UInt8>.allocate(capacity: byteCount)

Data to UnsafePointer

extension Data {
  func toPointer() -> UnsafePointer<UInt8>? {
    let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: count)
    let stream = OutputStream(toBuffer: buffer, capacity: count)

    stream.open()
    withUnsafeBytes({ (p: UnsafePointer<UInt8>) -> Void in
      stream.write(p, maxLength: count)
    })

    stream.close()

    return UnsafePointer<UInt8>(buffer)
  }
}

UnsafePointer to Data

extension UnsafePointer {
  func toData() -> Data {
    return Data(bytes: UnsafeRawPointer(self), count: 32)
  }
}

Dealing with C API

This is how to do keccak hash using C API from https://github.com/ethereum/ethash/blob/master/src/libethash/sha3.c

class KeccakHash {
  func hash(data: Data) throws -> Data {
    guard let dataPointer = data.toPointer() else {
      throw InteralError.invalid
    }

    let byteCount = 32

    let result = UnsafeMutablePointer<UInt8>.allocate(capacity: byteCount)
    sha3_256(result, byteCount, dataPointer, data.count)
    return result.toData()
  }
}

Read more

• See https://github.com/onmyway133/Reindeers/blob/master/Sources/Extensions.swift
• 
  How to import a C library in Swift using the Swift Package Manager